This invention relates to a locking device for wear-parts of tools for earth moving machines such as excavating machines, mechanical diggers, mechanical loaders, and dredgers etc. By wear parts for earth moving machines is meant teeth, cutting edges, front edges of scoops, road scraper blades, track shoes, etc. Common to all these wear-parts is that they are subjected to extreme wear by the material being worked and consequently they must be easy to replace. Usually the tools are therefore fitted with special holders into which the wear-parts proper are fitted. Even if the holders are only intended to be replaced in exceptional circumstances, they are usually regarded as wear-parts. The holders and the wear-parts proper are usually connected together by means of male and female units suited to each other and located in the area between the holder and the weap-part. When connected together the relative movement between the holder and the wear-part is locked by means of a locking device fitted in an opening running at right-angles to the direction of connection and formed for this purpose. In principle the locking device consists of a lock bolt and a lock catch which prevents the lock bolt from falling out after it has been fitted in place in the opening for this purpose. The lock catch can be an independent part fixed in the holder or the wear-part proper, or it can even be an integral part of the lock bolt. Most often the function of the lock catch is based on the elastic deformation of a piece of hard rubber or a steel spring. The elastic part of the lock catch is compressed when the lock bolt is forced into the opening for this purpose and it can be deformed again when the lock bolt is forced out of the opening. Normally this is done by driving the lock bolt in or out of the opening by means of blows from a heavy hammer. When the lock bolt is to be driven out, a mandrel is usually located between the lock bolt and the hammer. An example of a locking device with separate lock catch fixed in a holder is to be found in U.S. Pat. No. 2,427,651. The Swedish Pat. No. 333 551 shows a representative example of a locking device with a built-in lock catch.
Locking devices with built-in or separate lock catches can be made to function satisfactorily in most conditions, but in particularly adverse conditions it can happen that the lock catch is unable to prevent the lock bolt working its way out of the lock opening. Wear-parts are namely mass produced preferably by means of forging or casting with a minimum of machining afterwards and it is therefore practically impossible to avoid play between the parts at the same time as the parts are subjected to great forces and vibrations.